For the purpose of extending a layer 2 network or expanding the scale thereof, a packet may be sent using a plurality of types of network technology.
For example, in Patent Literature 1, an Ethernet (registered trademark) packet is sent using IP/MPLS (Internet Protocol/Multi Protocol Label Switching).
In the technology of Patent Literature 1, when a packet is relayed at an edge node, a transmission source MAC (Media Access Control) address of the packet is learned to build an address learning table.
Then, when a packet is to be relayed, a relay destination is determined based on this address learning table.
For a packet to a destination which has not been registered in the address learning table, a relay destination is investigated by flooding.
On the other hand, as a measure for preventing flooding for a packet to a destination which has not been learned, a technique may be considered in which two or more layer 2 switches constituting a layer 2 network mutually exchange MAC addresses each has learned, thereby building an address learning table.
For example, Patent Literature 2 discusses a technique in which two or more layer 2 switches mutually exchange MAC addresses each has learned, suggesting that an address learning table can be built without relaying a packet.